The present invention relates to a disk support device for supporting and driving a small-size disk such as a 3.5-inch magnetic disk, and more particularly to a disk support device capable of accurately positioning a disk at the time it is supported thereon.
One conventional type of disk support device is illustrated in FIGS. 1 and 2 of the accompanying drawings. The disk support device serves to drive a flexible magnetic disk which is 3.5 inches across.
The disk support device includes a rotatable drive shaft 1 which is rotated by a brushless motor (not shown) rotating at a constant speed, and a turntable 2 fixed to an upper end portion of the rotatable drive shaft 1. The rotatable drive shaft 1 has an upper end 1a projecting beyond an upper surface of the turntable 2. The turntable 2 has a hole 2a and an internally threaded hole 2b. A leaf spring 3 is mounted on a lower surface of the turntable 2 and has a central recess 3a defined therein and a support hole 3b defined in an end thereof. The leaf spring 3 has a positioning pin 4 fixed to an opposite end thereof. The rotatable drive shaft 1 is inserted in the recess 3a in the leaf spring 3. A fastening screw 5 is inserted through the support hole 3b threadedly into the internally threaded hole 2b to secure the corresponding end of the leaf spring 3 to the lower surface of the turntable 2. The positioning pin 4 projects upwardly out of the hole 2a beyond the upper surface of the turntable 2.
FIGS. 3 and 4 illustrate the manner in which a flexible magnetic disk 6 is mounted on the disk support device shown in FIGS. 1 and 2. Designated at 7 is a hub secured to a central portion of the magnetic disk 6. As shown in FIG. 3, the hub 7 has a central support hole 7a and another support hole 7b. When the magnetic disk 6 is mounted on the disk support device, the end 1a of the rotatable drive shaft 1 is inserted in the central support hole 7a and the positioning pin 4 is inserted in the other support hole 7b.
In operation, the turntable 7 is rotated clockwise in the direction of the arrow A by the rotatable drive shaft 1 to thereby rotate the hub 7 and the magnetic disk 6 in the direction of the arrow A. A magnetic head (not shown) is pressed against the magnetic disk 6 to record or reproduce information.
While the magnetic head is pressed against the magnetic disk 6, a resistance is imposed from the magnetic disk 6 on the magnetic head to bring an edge of the support hole 7b in the hub 7 into abutment against the positioning pin 4, which is then subjected to a force in the direction of the arrow B. Therefore, the positioning pin 4 tends to be tilted through an angle .alpha., thus deforming the leaf spring 3 as shown in FIG. 4.
When this happens, the hub 7 is displaced off the properly mounted position on the turntable 2. In general, one-pulse index signals are recorded at given positions on the magnetic disk in magnetic disk recording apparatus. The positions where such index signals are recorded must be accurate in order to ensure compatibility among the magnetic disk recording apparatus. If the magnetic disk 6 is displaced off position with respect to the turntable 2 as described above, then index signals will be generated at different positions, and compatibility among the magnetic disk recording apparatus will be lost.